Many types of suspensions and supports include a spring and a damping device to help isolate that supported from the support structure or surface. For example, automotive vehicles commonly use separate springs and simple shock absorbers to support the vehicle frame on the axle assemblies. Simple shock absorbers are typically oil-filled cylinders within which a vented piston is mounted. The piston is connected to a shaft which extends out of one end of the cylinder. The outer end of the shaft is mounted to one point on the vehicle and the other end of the cylinder is mounted to another point on the vehicle in parallel with the suspension spring. Thus, simple shock absorbers only provide damping and not support.
Another type of shock absorber, which is the type commonly used with motorcycles, off-road vehicles, competition automotive vehicles and off-road bicycles, combines both the suspension function and the shock absorbing function in one unit. This second type of shock absorber commonly uses a spring unit to provide the suspension function coupled with a damping unit to provide the damping function. Conventional shock absorber designs commonly incorporate an external coil spring, an internal air spring, or an internal bladder to provide the suspension function.
Typical shock absorbers (also referred to as shocks) provide two kinds of damping: compression damping (xe2x80x9cCDxe2x80x9d), and rebound damping (xe2x80x9cRDxe2x80x9d). One refers to damping force created during xe2x80x9cinwardxe2x80x9d travel of the shaft (shortening of the shock), the other refers to force created during xe2x80x9coutwardxe2x80x9d travel of the shaft (lengthening of the shock). Generally, but not alwaysxe2x80x94depending on linkage connecting shock to vehicle, RD applies during outward motion and CD applies during inward motion. Some shocks are externally adjustable by the user to provide for RD and/or CD adjustment.
Piston-type shock absorbers can be designed to provide the same amount of damping on both the compression stroke and the rebound stroke. Alternatively, the fluid passageways through the vented, damping piston can be designed so that the restriction to fluid flow through the damping piston during the compression stroke is different than the restriction to fluid flow during the rebound stroke. In this case the damping during the entire compression stroke is different than the damping during the entire rebound stroke.
Another type of damping is called position-sensitive damping. Position-sensitive damping is typically achieved by the combination of conventional vented piston damping, with the oil flowing through the damping piston, plus damping provided by the passage of oil around the damping piston through a bypass chamber or channel, which permits oil to bypass the piston during a portion of the piston stroke. The bypass channel thus permits lesser damping over the portion of the stroke during which some fluid flows around the piston through the bypass channel. Therefore, the shock can have different damping characteristics along different segments of the stroke. This is beneficial to the user because a single set of shocks can provide smooth damping for less aggressive riding and firm damping for aggressive riding without making any adjustments during the ride. For example, the shocks can provide reduced damping in the mid-stroke zone, where the shock is most active in, for example, trail riding or other less aggressive riding. If the rider starts riding more aggressively, or hits a large bump, causing the shock to compress deeper into the stroke, the bypass damping then becomes available and the shock relies on the conventional piston damping. This type of shock absorber has been available for many years. For example, a position-sensitive shock absorber has been sold by Fox Factory, Inc. of San Jose, Calif. since about 1987. U.S. Pat. No. 5,178,239 illustrates another example of a position-sensitive shock absorber. The position-sensitive damping action of the bypass channel is available during both the compression and rebound strokes.
The present invention is directed to shock absorbers, including position-sensitive shock absorbers in which the position-sensitive damping can be different during compression and rebound strokes, and shock absorbers with damping adjusters which vary the damping provided during compression and rebound strokes.
The position-sensitive shock absorber includes a cylinder within which a piston is movably mounted for movement between the first and second ends of the cylinder. First and second bypass openings open into the cylinder interior at axially spaced-apart positions. The bypass openings are coupled by a bypass channel. A flow valve is positioned along the bypass channel permitting fluid flow from the first opening to the second opening and restricting fluid flow from the second opening to the first opening. The first bypass opening may be selectively sealed by, for example, a movable closing member which is used to selectively cover or uncover the bypass opening. This selective sealing can be through the use of electromagnetic energy. Alternatively, the closing member can be biased to either cover or uncover the opening, the closing member overcoming the biasing force when a shock absorber is accelerated to an appropriate degree. The flow valve may also be a check valve.
Another aspect of the invention is directed to a position-sensitive shock absorber with a piston movably mounted within the cylinder for movement between the first and second ends of the cylinder. First and second bypass openings, coupled by a bypass channel, open into the cylinder interior. A pressurized gas container is fluidly coupled to the cylinder interior. A movable barrier separates the pressurized gas container from the cylinder interior. A shaft, having an inner end secured to the piston and an outer end extending out past the first end of the cylinder, is sealed by a shaft seal assembly. A spring element couples the shaft and the cylinder. This invention is also directed to a method for modifying the front forks in which any existing shock-absorbing components are removed from within the telescoping front forks of a wheeled vehicle and the above-described position-sensitive shock absorber is mounted within each telescoping front fork.
A further aspect of the invention is directed to a shock absorber including a cylinder with a piston movably mounted within the cylinder. A pressurized gas container is fluidly coupled to the cylinder interior and a movable barrier separates the pressurized gas container and the cylinder interior. A shaft has an inner end secured to the piston and an outer extending out past the first end of the cylinder. This shock absorber includes one or both of the following compression damping adjuster and/or rebound damping adjuster. The compressing damping adjuster includes a flow controller having a first path permitting substantially free fluid flow in a rebound direction from the movable barrier towards the piston and second flow path for fluid flow in a compression direction. The compression damping adjuster also includes an adjustable position flow restrictor situated along the second flow path to adjust the restriction to fluid flow in the damping direction. The rebound damping adjuster includes a rebound flow path through the piston and a rebound flow-restricting element movable to vary the restriction to rebound fluid flow along the rebound flow path. The shaft is a hollow shaft and the rebound flow-restricting element includes a rod housed within the hollow shaft. A rod position adjuster is mounted to the shaft and engages the rod so to adjust the axial position of the rod along the hollow shaft.
Other features and advantages of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawings.